How can a scientist determine if two species are obligate mutualists? The scientist should observe the species in the environment to determine the types of interactions that the two species have. Then, the scientist should transplant each species alone to a new area and simultaneously transplant both species together to see if the single-species transplants die. The scientist should observe the species in the environment, determine the types of interactions that the two species have, and then add an invading species to see if it outperforms one of the other species. The scientist should observe the species in the environment, determine the types of interactions that the two species have, and then transplant both species to a new location to observe if they do better or worse than the individuals in their old location. The scientist should observe the species in the environment, determine the types of interactions that the two species have, and then remove one of the species to see if the other species does not survive.